fix(editor): invalid caret in note-edgeless-block on focus (#14229)

### Problem
●In edgeless mode, when starting to edit, `note-block` exhibits two
types of invalid caret behavior:
(1)**Title Region Misalignment**: Clicking on the title region
incorrectly generates the caret in the first line of the note content,
rather than in the title itself.
(2)**Vanishing Caret at Line End**: When clicking in the empty space
beyond the end of a text section, the caret appears momentarily at the
line's end but disappears immediately.
●The following video demonstrates these issues:


https://github.com/user-attachments/assets/db9c2c50-709f-4d32-912c-0f01841d2024


### Solution
●**Title Click Interception**: Added a check to determine if the click
coordinates fall in the title region. If so, the caret positioning is
now handled by a dedicated logic path. Otherwise, it falls back to the
existing note-content logic as before.
●**Range Normalization**: When the generated `range.startContainer` is
not a `TextNode`, try to find a most appropriate `TextNode` and update
the `range` accordingly.

### After
●The video below shows the behavior after this fix.


https://github.com/user-attachments/assets/b2f70b64-1fc6-4049-8379-8bcf3a488a05



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Clicking a page block title no longer creates unwanted paragraphs and
reliably focuses the title.
* Paragraph creation now occurs only when needed and focus is applied
only after successful creation.
* Click coordinates are clamped to container bounds to prevent misplaced
cursors or focus.

* **Improvements**
* Caret normalization: clicks place the caret at the last meaningful
text position for consistent single-cursor behavior.

* **Tests**
  * Added end-to-end coverage for caret placement and focus transitions.
* New ratio-based click/double-click test utilities and a helper for
double-clicking note bodies.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/blocks/note/src/note-edgeless-block.ts

@@ -454,6 +454,28 @@ export const EdgelessNoteInteraction =
                     return;
                   }
 
+                  let isClickOnTitle = false;
+                  const titleRect = view
+                    .querySelector('edgeless-page-block-title')
+                    ?.getBoundingClientRect();
+
+                  if (titleRect) {
+                    const titleBound = new Bound(
+                      titleRect.x,
+                      titleRect.y,
+                      titleRect.width,
+                      titleRect.height
+                    );
+                    if (titleBound.isPointInBound([e.clientX, e.clientY])) {
+                      isClickOnTitle = true;
+                    }
+                  }
+
+                  if (isClickOnTitle) {
+                    handleNativeRangeAtPoint(e.clientX, e.clientY);
+                    return;
+                  }
+
                   if (model.children.length === 0) {
                     const blockId = std.store.addBlock(
                       'affine:paragraph',